The present invention relates to a communication apparatus and a communication system.
Data communication has recently become more and more important with the increasing use of the Internet, and its related applications. ATM networks in accordance with the ITU-T I.150 standard have been introduced in this field to integrate telephony and data communication. High-speed optical communication network technologies such as SONET defined by the ANSI T1.105 standard, SDH defined by the ITU-T G.707 standard, and OTN defined by the ITU-T G.872 standard have been introduced in this field. SONET and SDH have basically the same function, and OTN, an optical network, is based on the WDM (Wavelength Division Multiplexing) technology to raise the transmission capacity in a fiber.
These networks are interconnected by prescribing upper and lower layers based on the layer hierarchy of the OSI (Open System Interconnection) reference model defined by ISO. According to the provisions of these individual networks, ATM is ranked at the top; OTN is ranked at the bottom; and SONET and SDH are ranked at the middle. Each network is also of hierarchic structure, consisting of subnetworks. For example, an ATM network consists of a virtual path and a virtual channel, and SONET/SDH and OTN are of hierarchic structures, consisting of subnetworks, as well.